The invention relates to an electromagnetic linear drive which includes a first stator which constitutes a path of movement for a movable vehicle for a first running direction and a second stator which extends substantially parallel to the first stator and which constitutes a path of movement for a movable vehicle for the opposite direction. Each of the two stators includes current conductors or windings. Each stator is divided into a number of motor elements, and individual energy supply units adapted to be switched on and off individually are associated with the individual motor elements.
It is known in the prior art to divide the stator of an electromagnetic linear drive into a plurality of sections. A switching device is typically associated with each section to connect the current conductors of the respective section to an energy supply unit. As a result, energy need not be supplied simultaneously to all current conductors of the stator which constitutes the path of movement. If that were necessary, it would involve not only high losses in power but also require structural elements designed for high power. With known linear drive devices the individual sections of the stator are switched on and off by sensors which are disposed along the path of movement and which can be influenced by the movable vehicle. Thus the vehicle itself controls switching on and off of the individual sections of the stator.
Usually two paths of movement for opposite running directions are arranged side by side along a line.
It is an object of the invention to reduce the expenditure for components and circuitry and thus the overall cost of a magnetic transit system having paths of movement for opposite running directions disposed side by side.
This object is met, in accordance with the invention, in that each energy supply unit is associated with a motor element of one path of movement and the opposed motor element of the other path of movement and is connectable to the motor element of the one path of movement or the motor element of the other path of movement, as required. The common energy supply unit is connectable, according to a predetermined selection, to one of the two associated motor elements or alternatingly to one of the other of the two motor elements when a vehicle is located above both of the two motor elements associated with a single energy supply unit.
In this manner, half the number of energy supply units are sufficient with the present invention because a pair of opposed motor elements of the two paths of movement can be supplied by a common energy supply unit when the electromagnetic linear drive is designed in accordance with the present invention.
This design provides considerable savings in cost in view of the fact that expensive power components are generally needed for the energy supply units. This reduction to one half the number of energy supply units also permits great savings in circuitry expenditure and reduces the space necessary to house the energy supply units.
Various possibilities exist for the occasion when a vehicle is located above both motor elements belonging to one energy supply unit:
(1) One of two motor elements of a pair of motor elements associated with a common energy supply unit is selected and, in the instance described, the energy supply unit is connected to this motor element. No energy is supplied during this time to the other motor element of the pair;
(2) Both motor elements of this pair of motor elements are connected in an alternating manner to the energy supply unit;
(3) In each motor element the deviation of the actual speed from the instantaneous nominal speed is determined for the vehicle moving over the motor element. The enrgy supply unit is connected to the motor element for which a greater deviation from the nominal speed has been detected; or
(4) Neither of the two motor elements of such a pair of motor elements is connected to the energy supply unit so that both motor elements will remain passive and not transmit any pushing force to vehicles moving over the same.
The solution proposed by the instant invention is especially advantageous in connection with electromagnetic linear drives of which all motor elements are designed for the same maximum performance as claimed and described in detail in co-pending U.S. patent application Ser. No. 647, 706, entitled "An Electromagnetic Linear Drive", filed of even date herewith. With such a linear drive having equal performance motor elements all the energy supply units may be designed for the same maximum performance so that identical energy supply units can be utilized along the entire running line. Furthermore, the connection of a common energy supply unit to one or the other of the two motor elements of a pair of motor elements each designed for the same maximum performance is much simpler than would be the case with a pair of motor elements having individual motor elements designed for a different maximum performance.
The solution according to the present invention is also especially advantageous for use with an electromagnetic linear drive as disclosed in co-pending U.S. patent application Ser. No. 647,705, entitled "An Electromagnetic Linear Drive", filed of even date herewith. In that case running program numbers for the individual motor elements are stored in running program memories coordinated with the individual motor elements and may be called up in correspondence with the selection from a plurality of given running characteristics for the respective running line. The common energy supply unit of a pair of motor elements then will be controlled to supply power in accordance with the respective running program number selected of one or the other motor element of a pair of motor elements, depending on which of the two motor elements the energy supply unit is connected to.
An energy supply unit comprising monophase controllers designed according to co-pending U.S. patent application Ser. No. 647,707, entitled "An Energy Supply Unit For a Multiphase Electromagnetic Linear Drive", filed of even date herewith is especially well suited for a linear drive of the type described here, regardless of whether or not it includes equal performance motor elements and/or running program control.